The present application relates to multi-media networks, more particularly, to wirelessly transmission of a clock line for multimedia data distribution. The content of the distribution includes, but not limited to, high-definition video, digital sound, satellite TV, cable TV, high speed data, games, etc.
Note that the points discussed below may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.
With the proliferation of high quality video, an increasing number of electronic devices, such as consumer electronic devices, utilize high definition (HD) video which can require multi-Gbps (bits per second) in bandwidth for transmission. The High-Definition Multimedia Interface (HDMI) specification allows transfer of uncompressed HD signals between devices via a cable. While consumer electronics makers are beginning to offer HDMI-compatible equipment, there is not yet a suitable wireless (e.g., radio frequency) technology that is capable of transmitting uncompressed HD video signals.
The introduction of consumer friendly Wi-Fi technology has let home and office users create wireless local networks and connect two or more computers wirelessly to each other and a faster Internet line. This way there is no more poking holes in walls or tripping over Ethernet cables. People can access the internet anywhere in home and in office. The Wi-Fi technology is rapidly gaining acceptance as an alternative to a wired local area network (LAN).
A Wi-Fi enabled device such as a PC, game console, cell phone, MP3 player or a PGA can connect to the internet when within range of a wireless network that is connected to the Internet. The area covered by a Wi-Fi hotspot (Access Point) can be as little as a single room with wireless-opaque walls or as much as many square miles covered by overlapping access points.
Routers which incorporate a DSL or cable modem and a Wi-Fi access point are often used in homes and other premises, and provide Internet access and inter-networking to all devices connected via wireless or by cable into them. Devices supporting Wi-Fi can also be connected in ad-hoc mode for client-to-client connections without a router.
Wi-Fi devices use unlicensed spectrum to provide access to a network, ameliorating the trouble of obtaining FCC license.
In short, Wi-Fi allows LANs to be deployed without cabling for client devices, dramatically reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.
However, current Wi-Fi technology has significant operational limitations as well as severe shortcomings in spectrum assignments.
A current typical Wi-Fi adapter operates at a maximum raw data rate of 54 Mbit/s, and suffers sometimes severe channel interferences and collisions.
Given that the current high definition multimedia are transmitted as 1-10 Gbit/s, the current Wi-Fi system, with 54 Mbit/s capacity, is powerless to transmit high definition video, audio and other multimedia. Although current Ultra Wide Band technology can offer up to 5 Gbit/s, its range usually is within 10 meters, and often is Line of Sight.
In most wireless communications, HD video is first compressed before transmitting to the wireless medium. Compression of the HD video is attractive because the overall required communication bandwidth and power can be significantly reduced, relative to transmission of the original, uncompressed video. However, with each compression and subsequent decompression of the video, some video information can be lost and the picture quality is degraded. Wireless transmission of HDMI video/audio is key to operate a high quality home entertainment network.
Conventional HDMI cable contains multiple wired connections for data transfer including 1 wired line for CLOCK. This wire provides the source HDMI clock from a source, such as an HD DVD player to the destination HDMI clock, such as an HDMI plasma TV. This signal is required to synchronize the data for transfer and HDMI encryption. The HDMI cable connected between the source (e.g. DVD player) and the destination (e.g. TV) provides this CLOCK line. However, for a wireless system, where the DVD player is now connected to a wireless transmitter and the TV is connected to a wireless receiver, the CLOCK line is missing.
In most wireless system, data are transmitted as data packets. The access nodes obtain the data through a common IP multicast or broadcast group over an IP multicast network. Packets for the multicast or broadcast may arrive at the access nodes with differing delays due to non-synchronous nature of IP multicast or broadcast forwarding. Packets may also be non-synchronous because packets may be lost along the multicast forwarding path.